Method for preparing and catalytically cracking petroleum residuum fractions



Oct. 22, 1963 H H M E METHOD FOR PREPARING AND CATALYTICALLY CRACKING PETROLEUM RESIDUUM FRACTIONS Filed June 30, 1958 Dis "Ila flan Distillation lg lg Propane 2 l5 Devan/700mg! Crude OH I .Q Charging Sta k 23 Freda/0t fi e Cm c/rm g IN VEN TOR.

Herbert H. Meier,

A TTORNEX United States Patent METHQD FOR PREPARING AND CATALYTI- CALLY tllihiKItNG PETRiELEUh i RESIDUUIVH FRACTICNS Herhert El. Meier, La Porte, Tess, assigncr, by means assignments, to Essa Research and Engineering tCompany, Elizabeth, Nl, a corpcraticn of Delaware Filed Inns 30, 1053, S-er. No. 748,1d6 15 Claims. (Cl. 203-36) The present invention is concerned with the production of catalytically cracking feed stock of improved quality from crude petroleum residuum. By the use of the present invention, an increase in the yield and quality of gasoline and other desired products from crude petroleum may be obtained. In addition, the use of the present invention reduced the catalyst degradation in the catalytic cracking operations thereby enabling more effestive and economical utilization of the cracking catalyst.

Other objects and advantages of the present invention will be seen from the following description taken in conjunction with the drawing in which the sole FIG- U-RE is in the form of a diagrammatic flow sheet.

This application is a cont-inuation-in-part application of application S.N. 406,915 for Herbert H. Meier, filed January 29, 1954 now US. Patent No. 2,846,362.

In the process of the present invention a crude oil or mixture of crude oils is preliminarily distilled to recover a first residuum traction. This first residuum fraction is distilled to separate it into a distillate traction consisting of a major portion of the components of the first residuum and a second residuum fraction consisting of a minor portion of the components of the first residuum. The second residuum fraction is then propane deasphalted and the deasphalted second residuum admixed with the recovered distillate fraction and sent to a catalytic cracking process to recover catalytically cracked products.

Turning now specifically to the drawing, a crude oil charge stock which may be a single crude oil or mixture of crude oils is passed through inlet line 11 to distillation column 12. In distillation column 12, the charge stock is distilled to remove distillate fractions and a first residuum fraction. In the drawing, outlet lines 13 and 14 are shown for removing the distillate fractions and line 15 for removing the first residuum fraction. By way of specific example, the distillation column 12 may be operated so that the residuum is reduced at an equivalent atmospheric-pressure vapor temperature cut point of 850 F. and may be in the neighborhood of 20% of the total crude oil charged through inlet line i l.

The first residuum is passed through line 15 to second distillation step 16 Where it is separated into a distillate fraction and a second residual fraction. In the second distillation step conducted in column i6, the first residuum is distilled to an equivalent atmospheric-pressure vapor temperature 'in the range of 900 to 1200 F. so that at least a major portion of the first residuum fraction charged thereto is removed as a distillate fraction leaving as a second residual fraction a minor portion of the first residual fraction charged to said second distillation step. It is preferred that the second residual fraction be in the neighborhood of rd to Mith of the first residual fraction with the remainder removed as the distillate fraction from the second distillation zone. The second residual fraction is removed from distilla- Patented Get. 22, 1963 tion column 16 through line 17 and the distillate fraction is removed from distillation column 16 through line 1%.

The second residual fraction in line 17 is sent to propane deasphalting step 19. The use of propane for deasphalting residual oils is conventional to the art. By way of example, the deasphalting step may be carried out using a propane ratio in the range of from 2:1 to 10:1 at a temperature within the range of to 170 F. In order to simplify the description of the present application, the propane deasphalting step is indicated simply by a rectangle in the drawing with asphalt removed through outlet line 20.

The deasphalted second residuum is Withdrawn from propane deasphalting step 19 through line 21 and has admixed therewith the distillate fraction removed from the second distillation zone through line 18, the mixture then being sent to catalytic cracking step 22.

The use of catalytic cracking for cracking residual oils is well known to the art. In the drawing the step is indicated as a rectangle. Various alternative procedures are known to the art for carrying out catalytic cracking with the most common types involving the use of a synthetic clay or alumina silica type catalyst either arranged in fixed beds or in fluidized beds at a temperature in the range of 850 to 11-50 F. From the catalytic cracking step product is removed through outlet line 23. It will be understood that this product may be subjected to additional refining and treating steps if desired.

In order to illustrate further the practice of the present invention, the following illustrative example is given:

EXAMPLE A blend of crude oils comprising West Texas, Gulf Coast, Tomball, Salt Flat, East Texas, and Anahuac crudes was distilled employing steam to reduce partial pressure to obtain an equivalent atmospheric-pressure vapor temperature cut point of 850 From this distillation step an 18.3% residuum was produced. This 18.3% residuum was divided into two fractions, the first of which was propane deasphalted employing a propane to oil ratio of 4:1 and a temperature of F. The second fraction of the 18.3% residuum was vacuum distilled to produce a second 5.8% residuum, the 5.8% residuum was then deasphalted under the same conditions as used for the first fraction and the deasphaltedsec- 0nd residuumwas then blended with the overhead fraction. The characteristics and yields resulting from the treatment of said first and second fractions are set out in columns 1 and 2 in the following Table I:

1 Followed by blending of the deasphalted residuum and 81.794.2% overhead fraction in yield proportions.

3 63 Based on the properties of the material reported in Table I, predicted catalytic yields were then calculated. These predicted yields are set out hereafter in Table II:

1 Followed by blending of the deasphalted residuum and 8.1794.2% overhead traction in yield proportions.

-It will be observed from Table I that the yield of catalytic cracking feed stock produced by deasphalting the 18.3% residuum is approximately the same as that resulting when carrying out the present invention, namely distilling the first residuum to 5.8% bottoms, deasphalting the bottoms with a normally gaseous hydrocarbon solvent such as propane and then combining the deasphalted bottoms with the distillate fraction. However, the Conradson carbon and ash content of the catalytic cracking feed stock as shown in column 2 of Table I have been very sharply reduced, amounting to approximately /2 the corresponding values obtained when deasphalting the 18.3% residuum. This results in a substantially reduced catalyst degradation which, in general, is proportionate to the Conradson carbon and ash content of the feed stock.

From Table II it will be observed that the predicted yield of the desired C 430 F. naphtha fraction from the catalytic cracking of the feed stock in column 2 resulting from the process in accordance with the present invention is 54.8% as compared with a predicted yield of 51.8% from the feed stock produced by deasphalting the 18.3% residuum. Thus, it will be seen that an improved catalytic cracking feed stock is produced in accordance with the present invention.

I claim:

1. A method for treating petroleum fractions includ ing the steps of separating a first residuum fraction from a petroleum crude oil in a first distillation step with an equivalent atmospheric-pressure vapor temperature cut point of 850 F., vacuum distilling said first residuum fraction to separate a second residuum fraction consisting of approximately /3rd of said first residuum fraction and a distillate fraction consisting of the remainder of said first residuum fraction, propane deasphalting said second residuum fraction, combining the deasphalted second residuum fraction with said distillate fraction to form a cracking feed stock having a reduced Conradson carbon content, catalytically cracking the cracking feed stock and recovering catalytically cracked product.

2. A method for preparing a charge oil for catalytic cracking, which includes the steps of: heating an atmospheric reduced crude and introducing it into a vacuum flash tower at a temperature sufiiciently high to maintain a flash temperature within the range of about 200 F. below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25 of the oil present in said reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing sm'd cooled vacuum bottoms into a fractionation zone and countercurrently contacting said cooled vacuum bottoms therein with normally gaseous hydrocarbon solvent at temperatures within 100 F. of the critical temperature of t said solvent to fractionate said vacuum bottoms into an asphaltic ratfinate and a decarbonized oil extract having a Conradson carbon residue substantially lower than said vacuum bottoms; and employing the major parts of said vacuum distillate and said decarbonized oil in forming a catalytic cracking feed.

3. A method for preparing a charge oil for catalytic cracking, which includes the steps of: heating an atmospheric reduced crude and introducing it into a vacuum flash tower at a temperature sufficiently high to maintain a fiash temperature within the range of about 200 F. below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25% of the oil present in said atmospheric reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing said vacuum bottoms into a fractionation zone and countercurrently contacting said vacuum bottoms therein with a normally gaseous hydrocarbon solvent at temperatures within 100 F. of the critical temperature of said solvent to fractionate said vacuum bottoms into an asphaltic rafi'inate and a decarbonized oil extract having a Conradson carbon residue of less than half that of said vacuum bottoms; and combining said decarbonized oil extract with at least the major part of said vacuum distillate to form a catalytic cracking feed.

4. A method for preparing a charge oil for catalytic cracking which includes the steps of: heating an atmospheric reduced crude and flashing it under a pressure of less than 300 millimeters of mercury absolute pressure to produce a vacuum distillate comprising between 25% and of the oil suitable for catalytic cracking in said atmospheric residuum; cooling the bottoms resulting from the flashing of said atmospheric residuum and countercurrently contacting it with between 2 and 8 parts of normally gaseous hydrocarbon solvent at paracritical temperatures, recovering from said solvent contacting step a decarbonized oil extract having a Conradson carbon residue of less than half that of said bottoms; and forming a catalytic cracking feed employing at least the major parts of said vacuum distillate and said decarbonized oil.

5. The method as described in claim 4 in which said solvent contacting step is controlled to restrict the decarbonized oil extract produced thereby to a portion having a Conradson carbon residue of less than 10.

6. A method for preparing a charge oil for catalytic cracking which includes the steps of: heating an atmospheric reduced crude and flashing it under a pressure of less than 300 millimeters of mercury absolute pressure to produce a vacuum distillate comprising between 25 and 75% of the oil suitable for catalytic cracking in said atmospheric residuum and having a Conradson carbon residue of less than 0.5 weight percent; cooling the bottoms resulting irom the flashing of said atmospheric residuum and countercurrently contacting it at paracritical temperatures with between 2 and 8 parts of a solvent comprised primarily of a mixture of propane and butane; recovering from said solvent contacting step a decarbonized oil extract having a Conradson carbon residue of less than half that of said bottoms; and forming a catalytic cracking feed employing at least the major parts of said vacuum distillate and said decarbonized oil.

7.A method for preparing a charge oil for catalytic cracking, which includes the steps of distilling an atmospheric reduced crude in a vacuum distillation tower to an equivalent atmospheric-pressure vapor temperature in the range of 900 to 1200 F. to provide a vacuum distillate fraction comprising a major portion of said atmospheric reduced crude and a vacuum bottoms fraction comprising at least about 25 of said atmospheric reduced crude, introducing said vacuum bottoms into a fractionation zone and contacting said vacuum bottoms therein with normally gaseous hydrocarbon solvent to fractionate said vacuum bottoms into an asphaltic raifinate and a deasphalted oil extract having a Conradson carbon residue substantially lower than said vacuum bottoms; and employing at least the major part of said vacuum distillate and said deasphalted oil extract in donning a catalytic cracking feed.

8. A method for treating petroleum fractions including the steps of subjecting a petroleum crude oil to atmospheric pressure distillation to separate therefrom a first residuum fraction, vacuum distilling said first residuum fraction to an equivalent atmospheric pressure vapor temperature no less than 900 F. and below 1200 F. to separate a distillate fraction of at least a major portion of said first residuum fraction and a second residuum fraction or at least about 25% of said first residuum fraction, propane deasphalting said second residuum fraction, combining the deasphalted second residuum fraction with said distillate fraction to form a cracking feed stock having a reduced Conradson carbon content, catalytically cracking said cracking feed stock and recovering catalytically OlEtCifiCl product.

9. A method for preparing a charge oil for catalytic cracking, which includes the steps of: heating an atmospheric reduced crude and introducing it into a vacuum flash tower at a temperature sufliciently high to maintain a flash temperature within the range of about 200 F. below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25% of the oil present in said reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing said cooled vacuum bottoms into a fractionation Zone and contacting said cooled vacuum bottoms therein with normally gaseous hydrocarbon solvent at temperatures within 100 F. of the critical temperature of said solvent to fractionate said vacuum bottoms into an asphaltic raflinate and a decarbonized oil extract having a Oonradson carbon residue substantially lower than said vacuum bottoms; and employing the major parts of said vacuum distillate and said decarbonized oil in forming a catalytic cracking feed.

10. A method for preparing a charge oil for catalytic cracking, which includes the steps of: heating an atmospheric reduced crude and introducing it into a vacuum flash tower at a temperature sufficiently high to maintain a flash temperature below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25% oi" the oil present in said reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing said cooled vacuum bottoms into a fractionation zone and contacting said cooled vacuum bottoms therein with normally gaseous hydrocarbon solvent at temperatures within 100 F. of the critical temperature of said solvent to fractionate said vacuum bottoms into an asphaltic raffinate and a decarbonized oil extract having a Oonra-dson carbon residue substantially lower than said vacuum bottoms; and employing the major parts of said vacuum distillate and said decar-bonized oil in forming a catalytic cracking feed.

ll. A method for preparing a charge oil for catalytic cracking, which includes the steps of: heating an atmospheric reduced crude and introducing it into a vacuum flash tower at a temperature sufficiently high to maintain a flash temperature below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25% of the oil present in said atmospheric reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing said vacuum bottomsinto a fractionation zone and contacting said vacuum bottoms therein with a normally gaseous hydrocarbon solvent at temperatures within 100 F. of the critical temperature of said solvent to fractionate said vacuum bottoms into an asphaltic raiiinate d and a decarbonized oil extract having a Conradson carbon residue of less than half that of said vacuum bottoms; and combining said decarbonized oil extract with at least the major part or said vacuum distillate to form a catalytic cracking feed.

12. A method for preparing a charge oil for catalytic cracking, which includes the steps of 2 heating an atmospheric reduced crude and introducing it into a vacuum flash tower at a temperature sufii-ciently high to maintain a flash temperature below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25% of the oil present in said reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing said cooled vacuum bottoms into a fractionation zone and contacting said cooled vacuum bottoms therein with propane at temperatures within F. of the critical temperature of said propane to fractionate said vacuum bottoms into an asphaltic raflinate and a decarbionized oil extract having a Conradson carbon residue substantially lower than said vacuum bottoms; and employing the major parts of said vacuum distillate and said decarbonized oil in forming a catalytic cracking feed.

13. A method for prepming a charge oil for catalytic cracking, which includes the steps of: heating on atmos pheric reduced crude and introducing it into a vacuum flash tower at a temperature sufficiently high to maintain a flash temperature below that at which substantial thermal decomposition begins to take place; withdrawing a vacuum distillate from said tower; withdrawing from said tower a vacuum bottoms comprised of at least 25% of the oil present in said atmospheric reduced crude and suitable for catalytic cracking; cooling said vacuum bottoms, introducing said vacuum bottoms into a frationation zone and contacting said vacuum bottoms therein with propane at temperatures within 100 F. of the critical temperature of said propane to fractionate said vacuum bottoms into an asphaltic raffinate and a decarbonized oil extract having a Conradson carbon residue of less than hell that of said vacuum bottoms; and combining said decarbonized oil extract with at least the major part of said vacuum distillate to form a catalytic cracking feed.

14. A method which comprises the steps of distilling an atmospheric reduced crude in :a vacuum distillation tower to an equivalent atmospheric-pressure vapor temperature of at least 900 F. and below 1260" F. su'liicient to provide a vacuum distillate fraction comprising a major portion of said atmospheric reduced crude and a vacuum bottoms fraction comprising at least about 25% of said atmosphen'c reduced crude, introducing said vacuum bottoms into a fractionation zone and contacting said vacuum bottoms therein with a normally gaseous hydrocarbon solvent to fractionate said vacuum bottoms into an asphaltic raffinate and a deasphalted oil extract having a Connadson carbon residue substantially lower than said vacuum bottoms, combining at least a portion of the deasphalted oil with at least a portion of said vacuum distillate fr-ac-tion to form a catalytic cracking feed stock having a reduced Conradson carbon content, catalytically cracking said cracking feed stock and recovering catalytic-ally cracked products.

15. A method as in claim 14 wherein the selected temperature is suflicient to provide a vacuum bottoms fraction comprising between about one-third and about one-fourth of said atmospheric reduced crude.

References Cited in the file of this patent UNITED STATES PATENTS 2,528,586 Ford Nov. 7, 1950 2,685,561 Whitely et al Aug. 3, 1954 2,834,715 Pratt May 13, 1958 

8. A METHOD FOR TREATING PETROLEUM FRACTIONS INCLUDING THE STEPS OF SUBJECTING A PETROLEUM CRUDE OIL TO ATMOSPHERIC PRESSURE DISTILLATION TO SEPARATE THEEFROM A FIRST RESIDUUM FRACTION, VACUUM DISTILLING SAID FIRST RESIDUUM FRACTION TO AN EQUIVALENT ATMOSPHERIC PRESSURE VAPOR TEMPERATURE NO LESS THAN 900*F. AND BELOW 1200*F. TO SEPARATE A DISTILLATE FRACTION OF AT LEAST A MAJOR PORTION OF SAID FIRST RESIDUUM FRACTION AND A SECOND RESIDUUM FRACTION OF AT LEAST ABOUT 25% OF SAID FIRST RESIDUUM FRACTION, PROPANE 